1. Technical Field
The present invention relates to decorative components and, more particularly, to decorative automotive components having a molded elastomeric outer layer. The invention also relates to methods of making such decorative components.
2. Discussion of the State of the Art
A recent trend in the automobile industry has been the development of various non-fabric automotive trim components. Among the known systems for producing decorative components are polyvinyl chloride (PVC) vacuum and rotocast systems, thermoplastic polyolefin (TPO) vacuum formed systems, thermoplastic polyurethane (TPU) rotocast and sprayed aliphatic urethane systems generally. However, each of the foregoing systems present certain perceived drawbacks. For example, the known PVC vacuum form and rotocast systems are initially considered undesirable in that PVC is considered to be difficult to recycle and environmentally unfriendly, i.e., subject to releasing dioxins and other chlorinated by-products upon decomposition. Further, an unnecessarily thick skin is required to minimize the effects of plasticizer loss over time. PVC skins, particularly those which are vacuum formed, are often stiff and have a poor feel.
TPO vacuum formed systems are also often stiff and have a poor feel. Further, the grain definition of the resultant components are considered to be poor in quality. Additionally, TPO skins must often be coated to improve their resistance to scratch and mar resulting in increased costs and labor.
Accordingly, U.S. Pat. No. 5,116,577 to Dabaes et al. attempted to address many of the aforementioned drawbacks seen in PVC and TPO systems, as well as certain integral skin applications by developing a method for manufacturing mold components having a relatively low density, i.e., less than 700 g/dm3. The method is said to involve applying a layer of light stable polyurethane elastomer having a predetermined color onto a mold surface by spraying and thereafter injecting in the space of the mold cavity while the elastomer is still tacky a synthetic foam composition. Upon curing of both the elastomer layer and the synthetic foam, the resultant object is removed from the mold.
While the Dabaes patent arguably provides for an advancement in the art, certain perceived drawbacks are seen regarding its teachings. For example, the required use of a light stable aliphatic polyurethane elastomers for the external layer of the object is believed to greatly increase the cost of the resulting component. Further, the resulting elastomer often requires additional treatment to achieve adhesion to a urethane foam. Other perceived drawbacks include poor color matching with other components, poor fogging resistance, and poor feel due to the relatively thick skins that are typically achieved in practice.
In view of the foregoing, the compositions utilized to form the decorative components according to the methods of the present invention are believed to offer a significant cost savings, uniform color and gloss, excellent green strength and a high grain definition. The decorative components also exhibit excellent softness and feel and are generally resistant to runs and sagging. The elastomer compositions employed in accordance with the teachings of the present invention are readily processable and offer excellent adhesion to a variety of coatings and urethane foams used as backing layers.
According to a first aspect of the invention, a sprayable elastomer composition is described as comprising:
the reaction product of:
a) an aromatic isocyanate;
b) a solids containing polyol selected from the group consisting of graft polyols, polyisocyanate polyaddition polyols, polymer polyols, PHD polyols and mixtures thereof;
c) a polyol composition other than b); and
d) optionally one or more components selected from the group consisting of catalysts, chain extenders, defoamers, surface-active agents, adhesion promoters, flame retardants, anti-oxidants, water scavengers, dyes, ultraviolet light stabilizers, pigments, fillers, thixotropic agents and mixtures thereof;
wherein the solid contents of all components other than a) is up to 40.0 weight percent.
Preferably, the reaction product will include between about 5.0 weight percent to about 70.0 weight percent of a solid containing polyol based on the total amount of all components other than a).
According to another aspect of the present invention, a sprayable elastomer composition is disclosed as comprising:
a) an aromatic isocyanate;
b) a polyol composition including one or more polyols selected from the group consisting of polyether, polyester, polytetrahydrofuran, amine functional polyols and mixtures thereof, said polyol having a number average molecular weight of from about 100 to about 10,000;
c) optionally one or more components selected from the group consisting of catalysts, chain extenders, defoamers, surface-active agents, adhesion promoters, flame retardants, anti-oxidants, water scavengers, dyes, ultraviolet light stabilizers, pigments, fillers, thixotropic agents and mixtures thereof;
wherein said elastomer has an elongation after heat aging at 121xc2x0 C. for 500 hours of at least 150 percent.
According to another aspect of the invention, a method of making a decorative component in a mold cavity is disclosed as comprising the steps of:
a) applying a first coating composition having a predetermined color to said mold cavity;
b) applying an aromatic elastomer composition over said coating in said mold cavity and allowing said elastomer to cure to form an elastomeric layer; and
c) optionally demolding the resulting component.
Thereafter, either while the component remains in the mold cavity or after removal of the decorative component, a polyurethane foam composition having the desired density characteristics can be applied to the elastomeric layer to form a backing layer. Subsequent coating applications can also be applied over said first coating if desired.
Under an alternative method of the present invention, a decorative component can be formed in a mold having a mold cavity by the steps of:
a) applying an aromatic elastomer composition over a surface of said mold cavity and allowing said elastomer composition to at least partially cure to form an elastomeric layer;
b) introducing a polyurethane foam composition to said mold cavity and applying said foam composition to said at least partially cured elastomeric layer to form a backing layer on said component; and
c) demolding the resulting component.
A coating composition can then be applied to the elastomeric layer after the decorative component is demolded.
Additional benefits and advantages of the present invention will become apparent from a reading of the description of the preferred embodiments taken in conjunction with the specific examples provided.